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count subset of chars in a line

by GrandFather (Cardinal)
on Jun 22, 2005 at 03:36 UTC ( #468897=snippet: print w/ replies, xml ) Need Help??

Description:

Count all occurrences of characters from a given set in a string.

In the code below $CharSet is the set of characters to count. $SearchStr is the string to count them in.

my $Set = qr/[^$CharSet]/;
length join "", split $Set, $SearchStr;

Wrapped up in a rather more general sub:

sub CountSetChars
  {
  my $Count;
  my $CharSet = shift;
  my $Set = qr/[^$CharSet]/;
  my $Param;

  while ($Param = shift)
    {
    if (defined @$Param)
      {map {$Count += CountSetChars ($CharSet, $_)} @$Param;}
    elsif (ref $Param)
      {$Count += length join "", split $Set, @$Param;}
    else
      {$Count += length join "", split $Set, $Param;}
    }
  return $Count;
  }
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Re: count subset of chars in a line
by Zaxo (Archbishop) on Jun 22, 2005 at 03:49 UTC

    There's a very pretty way to count them with the tr// operator, my $vowel_count = tr/AEIOUYaeiouy//;
    If you want the character list in a variable, you need to string-eval:  my $foo_count = eval "tr/$foo//";

    After Compline,
    Zaxo

      Argh, I knew I'd seen a tidy way to do it somewhere. Sorting out the parameter handling for the sub was good exercise though :-).

      Perl is Huffman encoded by design.

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